FLEX的初始化顺序

FLEX组件在建立的时候都会经历四个事件：preinitialize,initialize,creationComplete 和 updateComplete（updateComplete事件在任何改动视觉的情况下都会发生，不是初始化时独有的）。

下面的例子检测在嵌套和平行的情况下，各个组件的事件抛出顺序。

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<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)">
<mx:script>
<!--[CDATA[
import flash.utils.getTimer;
private function showEvent(event:Event):void {
　　　　　　trace(flash.utils.getTimer().toString()+" >> "+event.currentTarget.name+" "+event.type);
}
　]]-->
</mx:script>
<mx:Canvas id="canv1"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)">
<mx:Button id="btn1"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)"/>
</mx:Canvas>
<mx:Button id="btn2"
preinitialize="showEvent(event)"
initialize="showEvent(event)"
creationComplete="showEvent(event)"
updateComplete="showEvent(event)"/>
</mx:Application>

<?xml version="1.0" encoding="utf-8"?><mx:Application xmlns:mx="http://www.a<a href="https://www.jb51.cc/tag/dob/" target="_blank" class="keywords">dob</a>e.com/2006/mxml" layout="absolute"preinitialize="showEvent(event)"initialize="showEvent(event)"creationComplete="showEvent(event)"updateComplete="showEvent(event)"> <mx:script>　　</mx:script> <mx:Canvas id="canv1"  preinitialize="showEvent(event)"  initialize="showEvent(event)"  creationComplete="showEvent(event)"  updateComplete="showEvent(event)">   <mx:Button id="btn1"  preinitialize="showEvent(event)"  initialize="showEvent(event)"  creationComplete="showEvent(event)"  updateComplete="showEvent(event)"/></mx:Canvas> <mx:Button id="btn2"  preinitialize="showEvent(event)"  initialize="showEvent(event)"  creationComplete="showEvent(event)"  updateComplete="showEvent(event)"/> </mx:Application>

上面的例子输出顺序是：

1299 >> eventTest0 preinitialize

1307 >> canv1 preinitialize

1310 >> btn1 preinitialize

1318 >> btn1 initialize

1319 >> canv1 initialize

1320 >> btn2 preinitialize

1321 >> btn2 initialize

1321 >> eventTest0 initialize

[SWF] G:/projects/eventTest/bin-debug/eventTest.swf - 588,818 bytes after decompression

1387 >> btn1 creationComplete

1387 >> btn1 updateComplete

1387 >> canv1 creationComplete

1387 >> canv1 updateComplete

1388 >> btn2 creationComplete

1388 >> btn2 updateComplete

1388 >> eventTest0 creationComplete

1390 >> eventTest0 updateComplete

看着有点混乱，不过仔细看看，可以把过程分成两个部分。

很明显，所有的creationComplete和updateComplete发生在第二次update的时候，之前flex组件只是做一些设置和计算的工作，并没有在画布上画任何东西。除此之外，还有这么一些规律：

就单个组件而言，事件的抛出顺序是preinitialize，initialize，creationComplete
嵌套关系的两个组件（比如Canvas和button1），preinitialize先外后内，initialize和creationComplete先内后外。只是creationComplete要在下一次update才会发生。
平行关系的两个组件（比如Canvas和button2），按mxml内的顺序，只有前面组件initialize结束后，后面的组件才会抛出preinitialize。

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